The steering of autotracing compact carrying vehicle such as golf cart is generally performed in either of the two methods. That is, in the first method, an RF signal transmitted from a transmitter carried by a player is received by two antennae carried on the cart and the steering is made by utilizing a difference in sensitivity between the two antennae. The other method utilizes a non-directional antenna and a directional antenna such as a loop antenna to utilize a difference in phase between the antennae. For the golf cart, the second method has been used widely because the electric field strength in the golf course area can not be uniform.
In the conventional system, the RF signal received by the loop antenna is fed to a 90.degree. phase shifter and the shifted signal is fed to a balanced modulator in which it is modulated by a rectangular wave. The modulated signal is mixed with the signal received by the non-directional antenna to obtain an IF signal which is detected by a detection circuit to obtain a pulse in phase or out of phase by 180.degree. by which the steering mechanism of the cart is controlled.
This method, however, is not effective if the electric field strength due to the RF signal is relatively weak and S/N ratio is low.
The conventional golf cart further includes an anti-collision device, which is in general, an ultra-sonic device, to prevent the cart from colliding with any obstacles. In this device, a sending transducer transmits an ultra-sonic wave and a receiving transducer receives an echo from an obstacle which is then detected to deenergize a drive motor.
This device, however, has a disadvantage that the receiving transducer often picks-up mechanical shocks and/or vibrations exerted on the cart body and provides pulse-like noises by which the load means such as drive motor which is to be deenergized by the output of the receiving transducer malfunctions.
In order to eliminate the above disadvantage, it is usual to provide a cushion material on the cart to thereby block the transmission of the shocks to the transducer. This procedure is not only complicated work but also not so effective.
An object of the present invention is to provide an improved autotracing carrying vehicle.
Another object to the present invention is to provide an improved direction sensor to be mounted on the vehicle.
Another object of the present invention is to provide an improved ultra-sonic anti-collision circuit to be mounted on the same vehicle.
Other objects and features of the present invention will become apparent by reading the description of the preferred embodiments of the present invention with reference to the attached drawings which are as follows.